Controlling self assembled monolayers

In this thesis, we demonstrate novel methods of controlling the morphology of self-assembled monolayers at the solution-graphite interface. Scanning tunneling microscopy is used to evaluate the capacity of chain length and weak dipolar interactions to direct packing and neighboring chain selection within monolayers. We designed and synthesized a series of 1,5-substituted anthracene derivatives and investigated the relationship between side chain structure and monolayer morphology. We report that the morphology of monolayers formed on HOPG from symmetrically substituted anthracene derivatives switches from a 2D racemate to a 2D conglomerate by the addition of a single methylene unit to each side chain, i.e., by changing the side chain lengths from even to odd.; We introduced ether groups into the side chains of anthracene derivatives in an attempt to use dipolar interactions to alter monolayer morphology. We report that the insertion of electronegative oxygen atoms into the side chains of anthracene derivatives can disturb the odd - even effect of chain length and influence monolayer morphology. By introducing a proper number of ether groups at specific side chain locations, we designed two self-repelling and complementary chains: COC12OC and C2OC10OC 2. COC12OC (or C2OC10OC2) chains repel themselves but select the other C2OC10OC 2 (or COC12OC) chains as their neighbors in self-assembled monolayers. Taking into account chain length matching and dipolar complementary as mechanisms for adjacent side chain selection, we designed and synthesized two symmetrical anthracenes 12 (COC12OC-An-COC 12OC), 13 (C2OC10OC2-An-C 2OC10OC2) and two unsymmetrical anthracenes 15 (C11OC-An-COC12OC) and 16 (C 18OC2-An-C2OC10OC2). Using a mixture solution of these molecules, we prepared a highly ordered AABB monolayer pattern in which paired rows of 15 alternate with paired rows of 16, and a highly ordered AAB monolayer pattern in which rows consisting of 12 are sandwiched between paired rows containing 16. The combination of chain length matching and dipolar complementary provides a potentially powerful strategy for producing controllably self assembled monolayers from multiple components at the liquid solid surface.; In monolayers formed from 1,5-substituted-anthracene derivatives, a number of monolayer defects were observed including isolated single and dimer defects, row defects and complicated interface defects. Packing models are proposed to explain the observed monolayer defects.; We designed and synthesized a series of 1,5-substituted-triptycene derivatives. We investigated the variation of STM image contrast for monolayers prepared from triptycene and anthracene derivatives with the tip-sample distance (or setpoint current/bias voltage). A model for the STM image contrast was explored.; Several triptycene diode molecules with long alkyl chains were designed and synthesized. Initial studies of their rectifying characteristics were performed on HOPG using scanning tunneling spectroscopy. Finally, we designed and synthesized a series of thioester prediode molecules for studies on gold surfaces. Initial studies of self-assembly on gold were performed using a series of related analogs.